Isolation protection circuit of 10-100kV high-voltage direct-current power supply and isolation protection method thereof

Abstract

The invention particularly relates to an isolation protection circuit of a 10-100kV high-voltage direct-current power supply and an isolation protection method of the isolation protection circuit, and solves the technical problem that a high-voltage rectifier bridge is damaged due to backflow impact of back voltage and large current when a load end of an existing high-voltage direct-current power supply is abnormal. The isolation protection circuit of the 10-100kV high-voltage direct-current power supply comprises a first-stage filter capacitor C1, a second-stage filter capacitor C2, an isolation inductor L and a current-limiting resistor R, the input end of the rectifier bridge is connected with high-frequency pulses; two ends of the first-stage filter capacitor C1 are respectively connected with an output high-voltage end and an output low-voltage end of the 10-100kV high-voltage direct-current power supply rectifier bridge; one end of the second-stage filter capacitor C2 is connected with the high-voltage output end of the rectifier bridge and one end of the current-limiting resistor R; one end of the isolation inductor L is connected with the low-voltage output end of the rectifier bridge, and the other end is connected with the other end of the second-stage filter capacitor C2 and the output ground; the other end of the current-limiting resistor R serves as an output positive end and is connected with a load; the method can realize safe and reliable isolation protection of the output end of the high-voltage direct-current power supply rectifier bridge.

Description

Technical Field

[0001] The invention specifically relates to an isolation protection circuit of a 10-100 kV high voltage direct current power supply and an isolation protection method thereof. Background Art

[0002] High-voltage DC power supplies have important applications in accelerators, pulse power technology, high-energy lasers, electrostatic dust removal, industrial waste gas and wastewater treatment, and other fields. High-voltage DC power supplies usually use transformers to increase the voltage to 10-100kV levels, and then use high-voltage rectifier bridges to rectify the high-frequency pulse current output by the transformer to achieve quasi-DC constant current output. High-voltage DC power supplies are usually used to charge high-voltage capacitors, high-voltage Max generators and other loads with constant current. Under normal circumstances, the output voltage of high-voltage DC power supplies is as high as 10-100kV, and its output constant current level is 0.5-10A; the rectifier diodes in the high-voltage rectifier bridges with nanosecond switching rates and withstand voltages greater than or equal to 1.7kV are commonly used, and the current level is 1-10A, and its forward non-repeatable surge current threshold is 20-100A, and the pulse width is ms-μs. When abnormal working conditions occur at the load end of the high-voltage DC power supply, such as the load capacitor short-circuiting and discharging to the ground, or the Max generator failing to trigger and discharge normally, a reverse voltage pulse current of hundreds of A to kA and a pulse width of μs will be formed at the output end of the high-voltage rectifier bridge of the high-voltage DC power supply, causing severe transient overcurrent shock to the high-voltage rectifier bridge, and even leading to serious accidents such as rectifier diode breakdown and high-voltage rectifier bridge short circuit.

[0003] In order to solve the problem of high-voltage rectifier bridge reverse voltage and high current impact, a high-voltage freewheeling diode with high current capacity is usually connected in reverse parallel between the positive and negative busbars of the high-voltage rectifier bridge output to conduct the high reverse voltage current directly from the freewheeling diode, thereby protecting the high-voltage rectifier bridge. However, in order to achieve 10-100kV high-voltage tolerance and hundreds of A-kA freewheeling capacity, the existing single diode cannot achieve this. It is necessary to use multiple high-voltage and high-current diodes in series and parallel to form a freewheeling diode module: the module is large in size and weight, and it is difficult to achieve lightweight and miniaturized integration with the high-voltage rectifier bridge; and the freewheeling diode module must consider the voltage and current sharing issues, which increases the technical difficulty. Another protection scheme is to connect a current limiting resistor in series on the output busbar of the rectifier bridge to reduce the peak value of the reverse voltage and high current through the current limiting resistor; however, if the current limiting resistor is too small, it will be difficult to achieve the protection function, and increasing the current limiting resistor will cause problems such as increased power charging loss and accumulated heat and explosion of the current limiting resistor. Therefore, the single protection scheme of the current limiting resistor cannot achieve safe and reliable protection of the high-voltage rectifier bridge. In addition, there is a solution to set up reverse voltage pulse current overcurrent measurement at the output end of the high-voltage rectifier bridge and control busbar cutting. The current measurement and timely feedback control of this solution are complex, difficult to implement, and have low reliability.

[0004] Therefore, how to explore a high-voltage DC power supply high-voltage rectifier bridge output isolation protection circuit method that is simple in principle, compact and lightweight, effective, feasible, safe and reliable, and greatly reduce the reverse pressure pulse current formed on the high-voltage rectifier bridge under abnormal conditions at the load end, so as to solve the problem of reverse pressure pulse current reflux impact damaging the high-voltage rectifier bridge and causing the rectifier bridge short circuit, is of great significance and practical value to improving the safety, reliability and service life of the high-voltage DC power supply. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problem that when there is an abnormality at the load end of the existing high-voltage DC power supply, the high-voltage rectifier bridge is damaged by the reverse voltage and large current backflow impact, and to provide an isolation protection circuit and an isolation protection method for a 10-100kV high-voltage DC power supply.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] An isolation protection circuit for a 10-100 kV high voltage DC power supply, which is special in that it includes a first-stage filter capacitor C1, a second-stage filter capacitor C2, an isolation inductor L and a current limiting resistor R;

[0008] The two ends of the first-stage filter capacitor C1 are respectively connected to the output high-voltage end and the output low-voltage end of the 10-100kV high-voltage DC power supply rectifier bridge;

[0009] One end of the second-stage filter capacitor C2 is connected to the output high-voltage end of the rectifier bridge and one end of the current-limiting resistor R;

[0010] One end of the isolation inductor L is connected to the output low voltage end of the rectifier bridge, and the other end is connected to the other end of the second-stage filter capacitor C2 and the output ground;

[0011] The other end of the current limiting resistor R is used as the output positive terminal and is connected to the load;

[0012] The value range of the first-stage filter capacitor C1 is 0.5 to 10 nF; the value range of the second-stage filter capacitor C2 is 1 to 10 nF; the value of the isolation inductor L is 100 to 500 μH; and the resistance value of the current-limiting resistor R is 100 to 500 Ω.

[0013] Furthermore, the withstand voltage of the first-stage filter capacitor C1 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge.

[0014] Furthermore, the withstand voltage of the second-stage filter capacitor C2 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge.

[0015] Furthermore, the first-stage filter capacitor C1 and the second-stage filter capacitor C2 respectively include a plurality of ceramic capacitors with a withstand voltage of DC40kV connected in series;

[0016] The isolation inductor L adopts an air-core inductor.

[0017] Furthermore, there are 4 ceramic capacitors with a withstand voltage of DC40kV;

[0018] The current limiting resistor R includes 20 2kΩ glass glaze resistors connected in parallel, and its power is greater than or equal to 50W.

[0019] At the same time, the present invention also provides an isolation protection method for a 10-100 kV high voltage DC power supply, which is based on the above-mentioned isolation protection circuit for a 10-100 kV high voltage DC power supply, and is special in that it includes the following steps:

[0020] A first-stage filter capacitor C1 is connected in parallel to the output high-voltage end and the output low-voltage end of the rectifier bridge of the 10-100kV high-voltage DC power supply, an isolation inductor L is connected in series between the output low-voltage end of the rectifier bridge and the output ground, a second-stage filter capacitor C2 is connected in parallel between the output high-voltage end of the rectifier bridge and the output ground, and a current-limiting resistor R is connected in series between the output high-voltage end of the rectifier bridge and the load, so as to achieve a maximum reverse voltage impact current pulse width of less than 2μs and an amplitude of less than 50A at the output high-voltage end of the rectifier bridge; wherein, the first-stage filter capacitor C1 and the second-stage filter capacitor C2 are respectively formed by connecting a plurality of DC40kV withstand voltage ceramic capacitors in series, and the current-limiting resistor R is formed by connecting a plurality of kΩ-level glass glaze resistors in parallel;

[0021] The value range of the first-stage filter capacitor C1 is 0.5 to 10 nF; the value range of the second-stage filter capacitor C2 is 1 to 10 nF; the value of the isolation inductor L is 100 to 500 μH; and the resistance value of the current-limiting resistor R is 100 to 500 Ω.

[0022] Furthermore, the withstand voltage of the first-stage filter capacitor C1 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge.

[0023] Furthermore, the withstand voltage of the second-stage filter capacitor C2 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge.

[0024] Furthermore, the first-stage filter capacitor C1 and the second-stage filter capacitor C2 are respectively formed by four ceramic capacitors with a withstand voltage of DC40kV connected in series; and the isolation inductor L is an air-core inductor.

[0025] Furthermore, the current limiting resistor R is formed by connecting 20 2kΩ glass glaze resistors in parallel, and its power is greater than or equal to 50W.

[0026] Beneficial effects of the present invention:

[0027] 1. The isolation protection circuit of the 10-100 kV high-voltage DC power supply of the present invention reduces the microsecond reverse voltage impact current amplitude of the diode of the high-voltage DC power supply rectifier bridge to less than 50 A under abnormal load conditions, thereby greatly improving the impact resistance of the high-voltage DC power supply rectifier bridge and the safety of the high-voltage DC power supply.

[0028] 2. The isolation protection circuit of the 10-100 kV high-voltage direct current power supply of the present invention realizes the current limiting and isolation functions through the two-stage filter capacitors (i.e., the first-stage filter capacitor and the second-stage filter capacitor) connected to the busbar at the output end of the high-voltage rectifier bridge, the series grounded isolation inductor L, and the series current limiting resistor R, thereby solving the problem of overcurrent impact on the high-voltage rectifier bridge caused by the reverse voltage large current under abnormal load conditions, resulting in damage and short circuit of the rectifier bridge.

[0029] 3. The isolation protection method of the isolation protection circuit of the 10-100kV high-voltage DC power supply of the present invention greatly reduces the difficulty of selecting diodes in the rectifier bridge of the high-voltage DC power supply, and realizes the miniaturization of the isolation protection circuit, and has a simple principle, stable and reliable, and low cost.

[0030] 4. The isolation protection method of the isolation protection circuit of the 10-100 kV high-voltage DC power supply of the present invention can realize safe and reliable isolation protection of the output end of the rectifier bridge of the high-voltage DC power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a schematic structural diagram of a high-voltage DC power rectifier bridge with isolation protection according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] like Figure 1As shown, an isolation protection circuit of a 10-100kV high-voltage direct current power supply comprises a first-stage filter capacitor C1, a second-stage filter capacitor C2, an isolation inductor L and a current limiting resistor R; two ends of the first-stage filter capacitor C1 are respectively connected to the output high-voltage end and the output low-voltage end of the 10-100kV high-voltage direct current power supply rectifier bridge; one end of the second-stage filter capacitor C2 is connected to the output high-voltage end of the rectifier bridge and one end of the current limiting resistor R; one end of the isolation inductor L is connected to the output low-voltage end of the rectifier bridge, and the other end is connected to the other end of the second-stage filter capacitor C2 and the output ground; the other end of the current limiting resistor R is used as the output positive end and is connected to the load; the value range of the first-stage filter capacitor C1 is 0.5-10nF; the value range of the second-stage filter capacitor C2 is 1-10nF; the value of the isolation inductor L is 100-500μH; the resistance value of the current limiting resistor R is 100-500Ω.

[0034] Preferably, the withstand voltage of the first-stage filter capacitor C1 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge. The withstand voltage of the second-stage filter capacitor C2 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge. The first-stage filter capacitor C1 and the second-stage filter capacitor C2 respectively include 4 series-connected ceramic capacitors with a withstand voltage of DC40kV; the isolation inductor L adopts a hollow inductor. The current-limiting resistor R includes 20 2kΩ glass glaze resistors in parallel, and its power is greater than or equal to 50W.

[0035] At the same time, the present invention also provides an isolation protection method for a 10-100kV high-voltage DC power supply. Based on the above-mentioned isolation protection circuit for a 10-100kV high-voltage DC power supply, the method comprises the following steps: connecting a first-stage filter capacitor C1 in parallel with the output high-voltage end and the output low-voltage end of the rectifier bridge of the 10-100kV high-voltage DC power supply, connecting an isolation inductor L in series between the output low-voltage end of the rectifier bridge and the output ground, connecting a second-stage filter capacitor C2 in parallel between the output high-voltage end of the rectifier bridge and the output ground, and connecting a current limiting resistor R in series between the output high-voltage end of the rectifier bridge and the load, so as to achieve The maximum reverse voltage impact current pulse width of the rectifier bridge output high voltage end is less than 2μs, and the amplitude is less than 50A; wherein, the first-stage filter capacitor C1 and the second-stage filter capacitor C2 are respectively composed of multiple DC40kV withstand voltage ceramic capacitors connected in series, and the current limiting resistor R is composed of multiple kΩ-level glass glaze resistors connected in parallel; the value range of the first-stage filter capacitor C1 is 0.5~10nF; the value range of the second-stage filter capacitor C2 is 1~10nF; the isolation inductor L has a value of 100~500μH; the resistance value of the current limiting resistor R is 100~500Ω.

[0036] In this embodiment, an existing DC80kV / 30kW high-voltage direct current power supply is subjected to output isolation protection processing according to the method of the present invention, as follows:

[0037] (1) Connect the first-stage filter capacitor C1 in parallel;

[0038] The first-stage filter capacitor C1 is connected in parallel between the high-voltage output end and the low-voltage output end of the DC80kV high-voltage DC power rectifier bridge; the first-stage filter capacitor C1 has a value of 2nF and is composed of 4 ceramic capacitors with a withstand voltage of DC40kV in series, and its withstand voltage reaches DC160kV;

[0039] (2) Connect isolation inductor L in series;

[0040] An isolation inductor L is connected in series to the negative output terminal of the first-stage filter capacitor C1; the isolation inductor L is in the form of an air-core inductor with a value of 100μH; the output positive terminal of the isolation inductor L is grounded;

[0041] (3) Connect the second-stage filter capacitor C2 in parallel;

[0042] The second-stage filter capacitor C2 is connected in parallel between the positive output terminal of the first-stage filter capacitor C1 and the positive output terminal of the isolation inductor L; the second-stage filter capacitor C2 has a value of 5nF ​​and is formed by connecting four ceramic capacitors with a withstand voltage of DC40kV in series, and the withstand voltage reaches DC160kV;

[0043] (4) Series current limiting resistor R;

[0044] A current limiting resistor R is connected in series at the positive end of the second-stage filter capacitor C2 output. The current limiting resistor R is formed by connecting 20 2kΩ glass glaze resistors in parallel. The current limiting resistor R is 100Ω and the power of the current limiting resistor R is 50W.

[0045] The existing DC80kV / 30kW high-voltage direct current power supply and output isolation protection circuit are connected to a 15-level Marx generator (i.e., load), and the high-voltage direct current power supply is used to perform a charge and discharge test on the 15-level Marx generator capacitor. When the Marx generator is operating under abnormal conditions, the maximum reverse voltage impact current pulse width formed on the diode of the rectifier bridge is 2μs and the amplitude is 45A; the rated current of the diode of the high-voltage direct current power supply rectifier bridge is DC5A, and the reproducible surge current amplitude is 75A and the pulse width is 10ms; after the high-voltage direct current power supply rectifier bridge diode is isolated and current-limited according to the method of the present invention, under the maximum reverse voltage large current impact, the rectifier bridge maintains safe and reliable operation without the risk of damage and short circuit. The test results prove that the method of the present invention solves the problem of overcurrent impact on the high-voltage rectifier bridge caused by reverse voltage large current under abnormal load conditions, resulting in damage and short circuit of the rectifier bridge.

[0046] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An isolation protection circuit for a 10-100 kV high voltage DC power supply, characterized in that: It includes a first-stage filter capacitor C1, a second-stage filter capacitor C2, an isolation inductor L and a current-limiting resistor R; The two ends of the first-stage filter capacitor C1 are respectively connected to the output high-voltage end and the output low-voltage end of the 10-100kV high-voltage DC power supply rectifier bridge; One end of the second-stage filter capacitor C2 is connected to the output high-voltage end of the rectifier bridge and one end of the current-limiting resistor R; One end of the isolation inductor L is connected to the output low-voltage end of the rectifier bridge, and the other end is connected to the other end of the second-stage filter capacitor C2 and the output ground; The other end of the current limiting resistor R is used as the output positive end and is connected to the load; The value range of the first-stage filter capacitor C1 is 0.5-10nF; the value range of the second-stage filter capacitor C2 is 1-10nF; the value of the isolation inductor L is 100-500μH; the resistance value of the current-limiting resistor R is 100-500Ω.

2. The isolation protection circuit of a 10-100 kV high voltage DC power supply according to claim 1, characterized in that: The withstand voltage of the first-stage filter capacitor C1 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge.

3. The isolation protection circuit of a 10-100 kV high voltage DC power supply according to claim 2, characterized in that: The withstand voltage of the second-stage filter capacitor C2 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge.

4. The isolation protection circuit of a 10-100 kV high voltage DC power supply according to claim 1, 2 or 3, characterized in that: The first-stage filter capacitor C1 and the second-stage filter capacitor C2 respectively include a plurality of ceramic capacitors with a withstand voltage of DC40kV connected in series; The isolation inductor L is an air-core inductor.

5. The isolation protection circuit of a 10-100 kV high voltage DC power supply according to claim 4, characterized in that: There are 4 ceramic capacitors with a withstand voltage of DC40kV; The current limiting resistor R includes 20 2kΩ glass glaze resistors connected in parallel, and the power thereof is greater than or equal to 50W.

6. A 10-100 kV high voltage direct current power supply isolation protection method, based on the 10-100 kV high voltage direct current power supply isolation protection circuit according to any one of claims 1 to 5, characterized in that: The following steps are involved: A first-stage filter capacitor C1 is connected in parallel to the output high-voltage end and the output low-voltage end of the rectifier bridge of the 10-100kV high-voltage DC power supply, an isolation inductor L is connected in series between the output low-voltage end of the rectifier bridge and the output ground, a second-stage filter capacitor C2 is connected in parallel between the output high-voltage end of the rectifier bridge and the output ground, and a current-limiting resistor R is connected in series between the output high-voltage end of the rectifier bridge and the load, so as to achieve a maximum reverse voltage impact current pulse width of less than 2μs and an amplitude of less than 50A at the output high-voltage end of the rectifier bridge; wherein, the first-stage filter capacitor C1 and the second-stage filter capacitor C2 are respectively formed by connecting a plurality of DC40kV withstand voltage ceramic capacitors in series, and the current-limiting resistor R is formed by connecting a plurality of kΩ-level glass glaze resistors in parallel; The value range of the first-stage filter capacitor C1 is 0.5-10nF; the value range of the second-stage filter capacitor C2 is 1-10nF; the value of the isolation inductor L is 100-500μH; the resistance value of the current-limiting resistor R is 100-500Ω.

7. The isolation protection method of a 10-100 kV high voltage DC power supply according to claim 6, characterized in that: The withstand voltage of the first-stage filter capacitor C1 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge.

8. The isolation protection method of a 10-100 kV high voltage direct current power supply according to claim 7, characterized in that: The withstand voltage of the second-stage filter capacitor C2 is greater than or equal to 1.5 times the maximum output voltage of the rectifier bridge.

9. The isolation protection method of a 10-100 kV high voltage DC power supply according to claim 6, 7 or 8, characterized in that: The first-stage filter capacitor C1 and the second-stage filter capacitor C2 are respectively formed by connecting four DC40kV withstand voltage ceramic capacitors in series; The isolation inductor L is an air-core inductor.

10. The isolation protection method of a 10-100 kV high voltage direct current power supply according to claim 9, characterized in that: The current limiting resistor R is formed by connecting 20 2kΩ glass glaze resistors in parallel, and its power is greater than or equal to 50W.

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